My left head light and running/tail light fuses are getting really hot. The don't blow they just sort of melt so its not like a direct short. what would be causing this?
Thanks

 

Wrong / under-rated fuses?
Wrong bulbs?
Drawing too many amps?

You could also try LED bulbs for less draw.

 

The bulbs i changed to oe and the fuses are the proper ones called for in the fsm. Ill change them to led for now but i have never had a fuse just melt over time like this. This is the problem with buying a car that some one has monkeyed with the wiring on

 

Check the parking light sockets for corrosion. Also consider getting the parking light relay kit from MSA and maybe even changing to LED bulbs for the parking lights.

 

Is there something wrong with these cars and the parking like wiring?

 

Your car is nearing 40 years old. Rubber gets old and degrades. Moisture builds. corrosion forms. The corrosion builds up to the point where it provides an alternate current path, dropping the resistance of the circuit gradually and increasing the current flow. Since the increase is gradual, it won't pop the fuse like you would want.

The problem is that the car is OLD.

 

Correct, if you bought a new car you wont have such problems but certainly other problems. An old man has aches in his joints young men don't unless he has abused himself. However wiring can be updated with mew ones and new technology as apposed to an old man not being able to swap out his old joints for new ones. Blame on the last guy who had the car is not even so correct as the owner or owners before him could have abused it. Go with new i would say !

 

Well i just thought since an entire kit was made for the parking light relays alone there was an inherent problem with that section of wiring or those relays. But you're all right i probably just need to freshen everything up.

 

The relay kits take stress off of the switches. Why is this important? Relays have a much higher resistance than the parking light circuit, and they have a lower inrush current than the parking light circuit.

The contacts on the combo switch see the current when you turn on the lights. Dust and debris will burn from the heat at the contacts, giving the contacts a light carbon coating. This coating will not conduct electricity very well and decreases the amount of surface area available on the contact to conduct electricity. This will cause more localized heating and carbon buildup. Enough of this, and the switch will heat up and act like a load. Since this load is in series with your lights, they will have less voltage and less light.

Power, and therefore heating is proportional to voltage and current. If you drop the current by using relays, you will not build up carbon on the switch contacts. This will greatly extend the life of the switch.

You can get a SPDT relay for about $5. A replacement used combo switch will cost $70 or more if it has been properly cleaned and tested. The relay will be new and will last a long time. You can even keep a spare or two in your glovebox.

I doubt the designers of the electrical system in the Z cars were worrying about problems creeping up in the electrical system 20, 30, or 40 years later. However, I will grant that most auto industry practices anymore include using relays on higher current circuits.

 

Wow, some great info right there. Thanks all you guys!
I just did some cleaning of the fuse holders and changed the relays and no more hear, also the lights are brighter.

 

I upgraded to the Dapper Lighting HID kit, back when it was first in group buy on HybridZ so I have full relays and everything for my headlights, but I also later found that the connector under the dash that goes to my light switch stalk was melted looking and was getting pretty warm/hot when the parking lights were on. I changed all the fuses and purchased the heavy duty parking light upgrade from MSA and all my lights are brighter, plus that connector no longer heats up.

 

It is still good to look for corrosion at the sockets and connectors to prevent the problem moving to another part of the harness.

 

If you take out the fuse block, ion the backside of the fuse block you will probably see that the wires that are crimped to the fuse holders are green or dark brown instead of shiny copper. This is a form of copper corrosion and what is happening is that the conducting area of the wire connection has gotten so small due to the corrosion, that you are actually conducting all of the current through a very small area, as if the 14 gauge wire were a 22 gauge wire. The smaller contact area has higher resistance and generates heat according to the equation I^2R, where I is the current and R is the net resistance, including the interference of the corrosion.

The traditional fix of using relays works because the control circuit of the relays draw less current than the lights that were there before. As the corrosion continues to build up, even the lesser current draw of the relay control circuit will cause the fuse holder to heat up and melt is self out of the plastic fuse panel.